This apparatus provides an electrical disconnecting switch which is incorporated into the motor terminal housing.
The National Electrical Code (NEC) as published by the National Fire Protection Association requires that "A [motor] disconnecting means shall be located in sight from the motor location and the driven machinery location." (NEC 430-102 (b). Thus, a mechanical means is required which can be used to electrically disconnect the machinery motor from the incoming electrical power lines, and must be located within a specified proximity to the motor and equipment which it disconnects.
This invention has incorporated a disconnecting switch of a type acceptable to the National Electrical Code into a housing which is adjacently affixed to the motor and which also serves as the required motor terminal housing wherein the incoming power lines are electrically connected to the electrical windings of the motor.
1. Background-Description of the Prior Art
Within the present art, electrical isolation of motors is generally achieved in one of two apparatus. In the first case, an electrical disconnect device is located within sight of the motor. Subsequently, the incoming electrical power lines to the motor are passed through, and may be de-energized by, the disconnect device.
In a second case, the disconnect device is distant from the motor location and may be incorporated into a motor control center. Provision is made within this remote location to de-energize the motor's incoming electrical power lines by means of a disconnecting device which can be locked in an open (de-energized) position.
In either case, the objective of the disconnecting device is to provide both protection to personnel and equipment during routine maintenance and ready access to a disconnecting means in the event of an emergency.
When properly installed according to the requirements of the National Electrical Code, the installation of a disconnecting device adjacent to the motor equipment being protected or in a motor control center provides the minimal required personnel and equipment protection. It has the disadvantage, however, of requiring an additional electrical device within the incoming electrical power lines servicing the motor. Further, it may be located such that it is not convenient for maintenance personnel to manipulate or verify during service.
The apparatus presented herein is a significant advance over the prior art in that it has incorporated the function of the electrical disconnecting device and the motor terminal housing into a single device affixed to the electric motor. The ensuing advantages of a disconnecting means which is affixed to the motor it is protecting is in the added safety of the disconnecting means immediately adjacent to the motor. In addition to safety advantages, economic advantages are gained by reducing the complexity of the electrical installation.
2. Objectives of the Invention
This apparatus was developed with an understanding of the limitations of the present technology employed in the electrical disconnecting means for an electric motor installation and., further, with a view to the requirements and intent of the National Electrical Code.
1. It is the general objective of this apparatus to provide a disconnecting means mounted directly to the electric motor which is served by the disconnecting means. PA1 2. Another objective of this apparatus is to integrate the disconnecting means and the motor terminal housing into a single enclosure, or adjoining enclosures. PA1 3. Another objective of this apparatus is to incorporate a means of disconnecting all incoming electrical power lines to the motor simultaneously with a single operator motion. PA1 4. Another objective of this apparatus is to provide a means for de-energizing the motor control circuit simultaneously and from the same location as the motor disconnect device. (The term simultaneously does not preclude the intended function of a control circuit break prior to the disconnection of the service leads.) PA1 5. Another objective of this apparatus is to provide a disconnecting device which will accommodate typical dual voltage and wye or delta wound alternating current motors. PA1 6. Another objective of this apparatus is to provide a disconnecting means for direct current motors. PA1 7. Another objective of this apparatus is to provide multiple embodiments of the disconnecting means. PA1 8. Another objective of this apparatus is to provide both a disconnecting means and a motor controlling means within a single enclosure affixed to an electric motor. PA1 9. A final objective of this apparatus is to provide a universal disconnecting device which may be adapted to individual manufacturers' motors by means of an adapter plate.
These and other objectives and advantages of the present apparatus, and the manner in which they are achieved, will become apparent in the following specifications and claims.